In a communication system, scheduling can be used in various meanings and mainly relates to efficient distribution of limited resources. For example, in case of uplink, scheduling is to determine as to when to transmit data through which user equipment using which channel resources (code, frequency, time, power, data rate, etc.). In case of downlink, scheduling is to determine as to whether a network provides services to which one of a plurality of user equipments for a specific time period at what level of Quality of Service (QoS), wherein the plurality of user equipments are receiving a specific service.
In downlink scheduling according to the related art, on the assumption that QoS requirements of all users are satisfied owing to sufficient network resource, there are provided scheduling algorithms that can satisfy the above requirements. However, since the network resource is not always sufficient, QoS requirements of all users are not always satisfied. Accordingly, it is necessary to consider what requirements for satisfying QoS of the users are under the circumstances that the network resource is not sufficient.
Furthermore, in order to actually realize and operate the scheduling algorithms at a desired level, it is necessary to determine as to whether QoS requirements of all users can be satisfied even in the case that a user who newly desires to enter a network is admitted to enter the network. If QoS requirements of all users are satisfied, the new user is admitted to enter the network. If not so, an action which does not admit network entrance of the new user is necessarily required. This is referred to as call admission control (CAC). A call admission control algorithm which is operated along with the scheduling algorithm has not been suggested until now.
However, the call admission control algorithm does not solve every problem due to time variable characteristics in resources of a radio channel. In other words, even though the call admission control algorithm determines that a user who newly arrives in the network is admitted to enter the network, a problem occurs in that the current status may be varied to the status where the user is not admitted to enter the network, as the time passes. However, the conventional scheduling algorithms fail to suggest preparations for the above problem.
Finally, a problem occurs in that the conventional scheduling algorithms do not handle as to how to use remaining resources after ensuring QoS of users. For this reason, this problem could lead to serious waste of radio resources under the circumstances that various types of QoS should be ensured.